Interaction between Nanoparticles, Membranes and Proteins: A Surface Plasmon Resonance Study.

Regardless of the promising use of nanoparticles (NPs) in biomedical applications, several toxic effects have increased the concerns about the safety of these nanomaterials. Although the pathways for NPs toxicity are diverse and dependent upon many parameters such as the nature of the nanoparticle and the biochemical environment, numerous studies have provided evidence that direct contact between NPs and biomolecules or cell membranes leads to cell inactivation or damage and may be a primary mechanism for cytotoxicity. In such a context, this work focused on developing a fast and accurate method to characterize the interaction between NPs, proteins and lipidic membranes by surface plasmon resonance imaging (SPRi) technique. The interaction of gold NPs with mimetic membranes was evaluated by monitoring the variation of reflectivity after several consecutive gold NPs injections on the lipidic membranes prepared on the SPRi biochip. The interaction on the membranes with varied lipidic composition was compared regarding the total surface concentration density of gold NPs adsorbed on them. Then, the interaction of gold and silver NPs with blood proteins was analyzed regarding their kinetic profile of the association/dissociation and dissociation constants (koff). The surface concentration density on the membrane composed of 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine and cholesterol (POPC/cholesterol) was 2.5 times higher than the value found after the injections of gold NPs on POPC only or with dimethyldioctadecylammonium (POPC/DDAB). Regarding the proteins, gold NPs showed preferential binding to fibrinogen resulting in a value of the variation of reflectivity that was 8 times higher than the value found for the other proteins. Differently, silver NPs showed similar interaction on all the tested proteins but with a variation of reflectivity on immunoglobulin G (IgG) 2 times higher than the value found for the other tested proteins.

Improvement of sensitivity of surface plasmon resonance imaging for the gas-phase detection of volatile organic compounds.

The analysis of volatile organic compounds (VOCs) is an important issue in various domains. For this, electronic noses (eN) are very promising as novel analytical tools that are portable, inexpensive, and efficient for reliable and rapid analyses. Recently, we have demonstrated that surface plasmon resonance imaging (SPRI) is especially interesting for the development of eNs dedicated for gas-phase analysis of VOCs. To further improve the performance of the eN based on SPRI, in this study, we investigated the influence of the LED wavelength on the sensitivity of the system. For this, a complete theoretical study together with a related experimental investigation for the validation were carried out. We have shown that the wavelength of the light source has an impact on the surface sensitivity of SPRI for the detection of VOCs. Indeed, in the studied wavelength range from 530 nm to 740 nm, both bulk sensitivity and surface sensitivity increase as the wavelength increases with good coherence between theoretical and experimental results. With the optimal LED wavelength, the detection limits of our eN reach low ppb range for VOC such as 1-butanol.

Highly sensitive olfactory biosensors for the detection of volatile organic compounds by surface plasmon resonance imaging.

Nowadays, monitoring of volatile organic compounds (VOCs) is very important in various domains. In this work, we aimed to develop sensitive olfactory biosensors using odorant binding proteins (OBPs) as sensing materials. Three rat OBP3 derivatives with customized binding properties were designed and immobilized on the same chip for the detection of VOCs in solution by surface plasmon resonance imaging (SPRi). We demonstrated that the proteins kept their binding properties after the immobilization under optimized conditions. The obtained olfactory biosensors exhibited very low limits of detection in both concentration (200 pM of ß-ionone) and in molecular weight of VOCs (100 g/mol for hexanal). Such a performance obtained with SPRi in solution is especially remarkable. We hypothesized that the binding of VOCs to the active sites of OBPs induced a local conformational change in the proteins. This change would give rise to a variation of refractive index, to which SPRi is extremely sensitive. In addition, the olfactory biosensors showed a high selectivity especially at relatively low VOC concentrations. With optimized regeneration procedures, they also showed very good repeatability not only from measurement to measurement but also from chip to chip with a lifespan up to almost two months. These olfactory biosensors are particularly interesting for trace detection of VOCs in solution.

Highly-Selective Optoelectronic Nose Based on Surface Plasmon Resonance Imaging for Sensing Volatile Organic Compounds.

Monitoring volatile organic compounds (VOCs) is an important issue, but difficult to achieve on a large scale and on the field using conventional analytical methods. Electronic noses (eNs), as promising alternatives, are still compromised by their performances due to the fact that most of them rely on a very limited number of sensors and use databases devoid of kinetic information. To narrow the performance gap between human and electronic noses, we developed a novel optoelectronic nose, which features a large sensor microarray that enables multiplexed monitoring of binding events in real-time with a temporal response. For the first time, surface plasmon resonance imaging is demonstrated as a promising novel analytical tool for VOC detection in the gas phase. By combining it with cross-reactive sensor microarrays, the obtained optoelectronic nose shows a remarkably high selectivity, capable of discriminating between homologous VOCs differing by only a single carbon atom. In addition, the optoelectronic nose has good repeatability and stability. Finally, the preliminary assays using VOC binary and ternary mixtures show that it is also very efficient for the analysis of more complex samples, opening up the exciting perspective of applying it to "real-world" samples in diverse domains.

Mode of PEG Coverage on Carbon Nanotubes Affects Binding of Innate Immune Protein C1q.

Surface modification of nanoparticles with poly(ethylene glycol) (PEG) is used in biomedicine to increase the circulation time of the particles after intravenous injection. Here, we study the interaction of PEG-covered carbon nanotubes (CNTs) with the serum complement protein C1q. Besides being the target-recognizing unit of the initiating complex for the classical pathway of complement in our innate immune system, C1q is involved in a range of important physiological processes. We modified the surface of multiwalled CNTs with covalently grafted PEG and physically adsorbed PEG. Transmission electron microscopy revealed the interaction of these PEG-coated CNTs with C1q. We found abundant C1q coverage on the PEG-grafted CNTs but not on the CNTs with adsorbed PEG. We tested the ability of these CNTs to activate the complement system using in vitro complement activation assays. None of the CNTs studied activated the C1q-dependent classical complement pathway. These findings are pertinent to the safe design and novel biomedical applications of PEGylated CNTs.